1//===-- X86TargetObjectFile.cpp - X86 Object Info -------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "X86TargetObjectFile.h"
11#include "llvm/ADT/StringExtras.h"
12#include "llvm/IR/Mangler.h"
13#include "llvm/IR/Operator.h"
14#include "llvm/MC/MCContext.h"
15#include "llvm/MC/MCExpr.h"
16#include "llvm/MC/MCSectionCOFF.h"
17#include "llvm/MC/MCSectionELF.h"
18#include "llvm/MC/MCValue.h"
19#include "llvm/Support/COFF.h"
20#include "llvm/Support/Dwarf.h"
21#include "llvm/Target/TargetLowering.h"
22
23using namespace llvm;
24using namespace dwarf;
25
26const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference(
27    const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
28    const TargetMachine &TM, MachineModuleInfo *MMI,
29    MCStreamer &Streamer) const {
30
31  // On Darwin/X86-64, we can reference dwarf symbols with foo@GOTPCREL+4, which
32  // is an indirect pc-relative reference.
33  if ((Encoding & DW_EH_PE_indirect) && (Encoding & DW_EH_PE_pcrel)) {
34    const MCSymbol *Sym = TM.getSymbol(GV, Mang);
35    const MCExpr *Res =
36      MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext());
37    const MCExpr *Four = MCConstantExpr::create(4, getContext());
38    return MCBinaryExpr::createAdd(Res, Four, getContext());
39  }
40
41  return TargetLoweringObjectFileMachO::getTTypeGlobalReference(
42      GV, Encoding, Mang, TM, MMI, Streamer);
43}
44
45MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol(
46    const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
47    MachineModuleInfo *MMI) const {
48  return TM.getSymbol(GV, Mang);
49}
50
51const MCExpr *X86_64MachoTargetObjectFile::getIndirectSymViaGOTPCRel(
52    const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
53    MachineModuleInfo *MMI, MCStreamer &Streamer) const {
54  // On Darwin/X86-64, we need to use foo@GOTPCREL+4 to access the got entry
55  // from a data section. In case there's an additional offset, then use
56  // foo@GOTPCREL+4+<offset>.
57  unsigned FinalOff = Offset+MV.getConstant()+4;
58  const MCExpr *Res =
59    MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext());
60  const MCExpr *Off = MCConstantExpr::create(FinalOff, getContext());
61  return MCBinaryExpr::createAdd(Res, Off, getContext());
62}
63
64const MCExpr *X86ELFTargetObjectFile::getDebugThreadLocalSymbol(
65    const MCSymbol *Sym) const {
66  return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
67}
68
69void
70X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx,
71                                         const TargetMachine &TM) {
72  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
73  InitializeELF(TM.Options.UseInitArray);
74}
75
76const MCExpr *X86WindowsTargetObjectFile::getExecutableRelativeSymbol(
77    const ConstantExpr *CE, Mangler &Mang, const TargetMachine &TM) const {
78  // We are looking for the difference of two symbols, need a subtraction
79  // operation.
80  const SubOperator *Sub = dyn_cast<SubOperator>(CE);
81  if (!Sub)
82    return nullptr;
83
84  // Symbols must first be numbers before we can subtract them, we need to see a
85  // ptrtoint on both subtraction operands.
86  const PtrToIntOperator *SubLHS =
87      dyn_cast<PtrToIntOperator>(Sub->getOperand(0));
88  const PtrToIntOperator *SubRHS =
89      dyn_cast<PtrToIntOperator>(Sub->getOperand(1));
90  if (!SubLHS || !SubRHS)
91    return nullptr;
92
93  // Our symbols should exist in address space zero, cowardly no-op if
94  // otherwise.
95  if (SubLHS->getPointerAddressSpace() != 0 ||
96      SubRHS->getPointerAddressSpace() != 0)
97    return nullptr;
98
99  // Both ptrtoint instructions must wrap global objects:
100  // - Only global variables are eligible for image relative relocations.
101  // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
102  const auto *GOLHS = dyn_cast<GlobalObject>(SubLHS->getPointerOperand());
103  const auto *GVRHS = dyn_cast<GlobalVariable>(SubRHS->getPointerOperand());
104  if (!GOLHS || !GVRHS)
105    return nullptr;
106
107  // We expect __ImageBase to be a global variable without a section, externally
108  // defined.
109  //
110  // It should look something like this: @__ImageBase = external constant i8
111  if (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" ||
112      !GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() ||
113      GVRHS->hasSection())
114    return nullptr;
115
116  // An image-relative, thread-local, symbol makes no sense.
117  if (GOLHS->isThreadLocal())
118    return nullptr;
119
120  return MCSymbolRefExpr::create(TM.getSymbol(GOLHS, Mang),
121                                 MCSymbolRefExpr::VK_COFF_IMGREL32,
122                                 getContext());
123}
124
125static std::string APIntToHexString(const APInt &AI) {
126  unsigned Width = (AI.getBitWidth() / 8) * 2;
127  std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
128  unsigned Size = HexString.size();
129  assert(Width >= Size && "hex string is too large!");
130  HexString.insert(HexString.begin(), Width - Size, '0');
131
132  return HexString;
133}
134
135static std::string scalarConstantToHexString(const Constant *C) {
136  Type *Ty = C->getType();
137  if (isa<UndefValue>(C)) {
138    return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
139  } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
140    return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
141  } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
142    return APIntToHexString(CI->getValue());
143  } else {
144    unsigned NumElements;
145    if (isa<VectorType>(Ty))
146      NumElements = Ty->getVectorNumElements();
147    else
148      NumElements = Ty->getArrayNumElements();
149    std::string HexString;
150    for (int I = NumElements - 1, E = -1; I != E; --I)
151      HexString += scalarConstantToHexString(C->getAggregateElement(I));
152    return HexString;
153  }
154}
155
156MCSection *X86WindowsTargetObjectFile::getSectionForConstant(
157    const DataLayout &DL, SectionKind Kind, const Constant *C) const {
158  if (Kind.isMergeableConst() && C) {
159    const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
160                                     COFF::IMAGE_SCN_MEM_READ |
161                                     COFF::IMAGE_SCN_LNK_COMDAT;
162    std::string COMDATSymName;
163    if (Kind.isMergeableConst4() || Kind.isMergeableConst8())
164      COMDATSymName = "__real@" + scalarConstantToHexString(C);
165    else if (Kind.isMergeableConst16())
166      COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
167
168    if (!COMDATSymName.empty())
169      return getContext().getCOFFSection(".rdata", Characteristics, Kind,
170                                         COMDATSymName,
171                                         COFF::IMAGE_COMDAT_SELECT_ANY);
172  }
173
174  return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C);
175}
176